In the last 80 years, the aircraft industry has made wide use of load bearing skins in what is called monocoque or semi-monocoque construction of both wings and fuselages. In such a construction method, the outside skin of the aircraft is an integral structure that is stabilized against buckling and able to carry the major air loads, bending loads and pressurization loads. Local concentrated loads, such as wing to fuselage attachments, drivetrain to airframe attachments and landing gear attachments, are distributed to the skins through use of bulkheads and other internal structural members.
Propeller driven aircraft traditionally use internal frames and/or pylon structures to carry the load from the gearbox-engine assembly to the wing or the nose of the aircraft. In such cases the powerplant is enclosed by a non-structural cowling that provides the desired external aerodynamic shape and internal air flow. While the non-structural cowling over internal frame construction provides easy access for maintenance, the cowling is heavy as compared to a single load-bearing monocoque.
Vertical Take-Off and Landing (VTOL) aircraft and Short Take-Off and Landing (STOL) aircraft have for many years also used internal frames and/or pylon structures to carry the load from the propeller-gearbox-engine assembly to the fuselage of the aircraft. See, for example, WO 96/11843 to Brodell (publ. April 1996), and U.S. Pat. No. 4,658,579 to Bower et al. (April, 1987). These and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
The rotors of a VTOL or STOL aircraft can apply large lift, torque and moment loads to their support structures. This is especially true of a rigid or hingeless rotor. In these demanding VTOL and STOL configurations where weight is a critical factor, traditional pylon and internal frame supports would be structurally inefficient because they would require significant additional material to provide adequate structural stiffness and strength.
Thus, there is still a need for better ways of transferring loads from a propeller-gearbox-engine assembly to the fuselage of an aircraft.